Abstract
Three genes coding for small, acid-soluble spore proteins (SASP) were cloned from Bacillus megaterium, using previously cloned B. megaterium SASP genes (SASP-C and -C-3) as DNA-DNA hybridization probes. One gene (SASP-A) codes for the A protein, a previously identified major SASP. The other two (termed genes for SASP-C-4 and -C-5) are extremely similar in much of their nucleotide sequence to the previously cloned B. megaterium SASP-C-2 gene. The proteins coded for by all these SASP genes had extensive sequence homology with each other and with those coded for by the B. megaterium SASP-C, -C-1, -C-2, and -C-3 genes. Their coding sequences are preceded by strong ribosome-binding sites and are followed by regions of dyad symmetry which presumably are transcription stop sites. The SASP-A, -C-4, and -C-5 genes are expressed in parallel during sporulation, and their transcription start points were localized by the size of the mRNAs produced. The sequences localized 10 and 35 base pairs upstream from the transcription start points show significant homology with the analogous regions of the SASP-C, -C-1, -C-2, and -C-3 genes. The identification of seven closely related SASP genes in B. megaterium indicates that the SASP are the products of a very extensive multigene family.